Which is TRUE about y + 3 = 9?
A) y + 3 = 9 is an equation because you can solve for y.
B) y + 3 = 9 is an expression because there is an equal sign.
C) y + 3 = 9 is an equation because y has more than one value.
D) y + 3 = 9 is an expression because it has only one variable